Prophylactic devices, such as condoms, finger cots, and gloves, such as examination and surgical gloves, are typically made of polymeric materials to provide protection against chemicals, abrasions, germs, viruses, and microbes among many uses. Polymeric materials include natural rubber latex (natural polyisoprene), synthetic polyisoprene, or various polyurethanes. Prophylactic devices made of natural rubber are strong. Natural rubber, sourced from Hevea Brasiliensis and/or guayule, has a high level of stereo-regularity, meaning that the polymer molecules of which it is comprised consist almost exclusively of cis-1,4 isoprene units. Natural rubber latex is also a highly branched polymer with a high molecular weight and a wide molecular weight distribution. These characteristics of the natural rubber result in vulcanized rubber products having a unique combination of strength and elasticity. However, natural rubber also contains proteins that produce dermal allergic reactions in some susceptible individuals.
Synthetic polyisoprene resins have been developed to provide the benefits of natural rubber and to eliminate the potential for protein allergy. However, some synthetic polyisoprenes, such as that produced by Kraton Inc., by anionic addition polymerization, typically consist of lower levels of stereo-regularity (i.e., less than 90% cis 1,4 isoprene) and reduced molecular weight. Consequently, articles produced from such synthetic polyisoprenes have inferior properties compared with natural rubber articles. In addition, synthetic polyisoprene latex with lower levels of stereo-regularity unfavorably flocks and agglomerates in suspension, which results in defects in dipped articles. A latex dip tank of such a synthetic polyisoprene correspondingly has a limited available processing window for dipping articles. Furthermore, addition of anti-flocculants interferes with cross-linking, resulting in anisotropic cure properties, e.g., poor strength and elongation properties, such as voids and cracks due to the formation of fractures in inter-particle and intra-particle regions.
There is an ongoing need to produce prophylactic devices, such as condoms, finger cots, and polymeric gloves that are thin, strong and non-allergenic.